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Onan Generators

Onan Mdja 3.0 Separating Gen from Engine


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  #1  
Old 04-27-2017, 10:37:39 PM
actionjacksonbn actionjacksonbn is offline
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Default Onan MDJA 3.0 advice would be great

So I just picked up an Onan mdja 3.0 that hadn't been ran in years for $300 dollars. First things first I got it home excited to mess with it and noticed that I saw no starter so I assumed (luckily correctly) that the 4 gauge or so wires coming from the generator end would definitely lead to internal windings and sure enough she spun not fast by any means. And thanks to the all mighty google it led me to you guys learning about the decompression solenoid that is of course bad so I have been manually operating it. Well today I got her running. She seems to be spinning pretty fast however I'm not positive if she is spinning a true 1800 as I do not know what leads to attach to. The only way I know of telling if it is spinning a true 1800 is by measuring frequency. Basically I purchased this generator with the engine and gen separated from the control box. I do have the control box and it appears it hasn't been torn apart just simply a few wires clipped to remove it from the gen. So I have overall 5 leads coming off the gen end. I have two wires for starting that are approximately 4 gauge and I have three smaller gauge wires two appear to be 10 gauge and one appears to be 12 or 14 gauge and it appears to match up with one of the clipped wires in the control box. Are my other two 10 gauge leads the power leads that would feed the panel? I was only getting 39-42 volts when I hooked my meter to them earlier.Click image for larger version

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  #2  
Old 04-28-2017, 03:36:30 AM
Ray Lynch Ray Lynch is offline
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Default Re: Onan MDJA 3.0 advice would be great

Welcome to the site.
Please post full model and serial number to help get the answers you need.
Manuals can be found in the attached link. Start looking from around 968-xxxx on down for MDJA manuals.
Ray

http://www.twinslan.net/~n0nas/manuals/onan/
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Old 04-28-2017, 10:28:55 AM
actionjacksonbn actionjacksonbn is offline
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Default Re: Onan MDJA 3.0 advice would be great

Where can I find the model number? there is a cast number on the side of the block but there appears to be a missing plate on the side side of the generator end
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Old 04-28-2017, 11:25:36 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan MDJA 3.0 advice would be great

Look for six numbers stamped into the block. That will be the serial number. With them we can get you the information you need.
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Old 04-28-2017, 11:51:07 AM
Ray Lynch Ray Lynch is offline
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Default Re: Onan MDJA 3.0 advice would be great

Try this.
Ray

https://www.smokstak.com/forum/showthread.php?t=104361
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Old 04-28-2017, 01:23:38 PM
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Talking Re: Onan MDJA 3.0 advice would be great

What would you like to know? I have 2 MDJA Gensets, and a DJA contractor version.... They are great little Diesel GenSets and sip fuel very nicely, even at Full Rated Load.... A small Foreign Car Radiator, in the Secondary Cooling Loop, works just fine for Cooling, or with a little Engineering, One can make a CoGeneration Setup to use the Cooling BTUs as an external Heat Source for all kinds of applications.... With a bit more engineering, one can recover about 50% of the Exhaust BTUs for CoGen purposes....
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Old 04-30-2017, 11:00:06 AM
actionjacksonbn actionjacksonbn is offline
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Default Onan Mdja 3.0 Separating Gen from Engine

So my previous question about the mdja I was able to solve and I got everything put back together and she's running like a dream .... minus the manual operation of the decompression switch. However, my next question is coming to the install of this gen into the boat. The hatch I need to go through is a tad to small also once in the bilge this thing is going to be extremely hard to maneuver due to the weight. So I would like to separate the gen from the engine. Have any of you guys done this? There don't appear to be any visible outside bolts. Does anybody have some insight to the difficulty factor of this? Also I'll be posting a video of my mdja running soon!

Last edited by BTPost; 04-30-2017 at 12:30:44 PM. Reason: PLEASE keep to a single Thread on any ONE Unit... OK?
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Old 05-02-2017, 04:42:22 PM
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Default Re: Onan Mdja 3.0 Separating Gen from Engine

https://www.youtube.com/watch?v=kwMYqvQQ_gk video of her running
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